NEWARK — When Alexander Alfaro’s murder trial started earlier this month, the assistant prosecutor pointed to a timid-looking young man at the defense table, saying he had savagely attacked Iofemi Hightower with a machete before she and two friends were fatally shot execution-style — and another wounded — at a Newark schoolyard.

"We know what he did, ladies and gentleman, from his own lips," Essex County assistant prosecutor Thomas McTigue told the Superior Court jury. McTigue said he would play a taped statement Alfaro made to police after the Aug. 4, 2007, triple killing behind Mount Vernon School, in which he admits to wielding the machete.

Alfaro, now 20, was one of six young men charged in the killings.

In the days that followed that opening salvo, Alfaro’s alleged involvement has barely been mentioned.

That changed Tuesday, when prosecutors for the first time sought to directly link him to the crime during testimony by a forensic pathologist who conducted the autopsy on Hightower.

The doctor, Edward Chmara, pointed to an enlarged autopsy photograph of Hightower as he described the two long "chopping" wounds on one side of her head, a large cut to her hand and a deep gash extending past her ear. The force of that blow, Chmara said, nearly severed the ear.

"I knew from the time we saw these that we were looking for a machete," he told McTigue on direct examination. That statement came on a day in which prosecutors showed autopsy photos of all three victims, who doctors said were shot at point-blank range in the base of the skull and died almost instantly.

Hightower and Dashon Harvey, both 20, and Terrance Aeriel, 18, were lined up against a wall before they were shot. Terrance’s sister, Natasha, who was 19, was shot but survived.

On cross-examination, defense attorney Raymond Morasse sought to cast doubt on Chmara’s machete claim. He pointed to the fact that the doctor never noted the type of weapon on his autopsy report. Chmara said he told detectives in the room that day, but left it off the report because he isn’t an expert in that area of science.

The 23-inch machete, which was discovered in the schoolyard days after the killing, has been brought out several times in court, if only briefly. Blood stains found on the blade were matched to Hightower, though no fingerprints could be lifted from the rusted, cracked weapon. No physical evidence has linked Alfaro to the crime, and prosecutors have yet to play his statement to police.

Another witness who testified Tuesday, Steven Symes, a forensic anthropologist, said he could not be certain the machete blade authorities recovered caused Hightower’s wounds — which included several puncture marks to her back and slashes to her arm — but said the injuries fit a similar classification of weapon.

Prosecutors allege Alfaro was ordered to bring the weapon to the schoolyard by his half-brother, Rodolfo Godinez, who was also charged in the killing. Authorities say the six young men — all with alleged ties to a violent Central American street gang — set upon the college-bound friends who were in the schoolyard listening to music.

Godinez, 27, was convicted at trial last spring. In September, another defendant, Melvin Jovel, 21, admitted he shot all four victims. Both men had made statements to police after their arrests. Both are serving life sentences.